1. Field of the Invention
The present invention relates to a mobile communication system, and in particular to a mobile communication system composed of a private branch exchange (hereinafter occasionally abbreviated as PBX) connected to a mobile communication network through an interface unit and having a semi-public roaming function.
In recent years, with the semi (quasi)-public roaming function by which a public PHS (hereinafter simply referred to as PHS) as a mobile station can have services equal to those in the mobile communication network through a base station within the PBX, utilities of the PHS have been spread. It is important to certainly perform a position registration, a call transmission and a call reception between the PHS and the mobile communication network so that the PHS may have the services equal to those in the mobile communication network.
2. Description of the Related Art
FIG. 52 shows an arrangement of a prior art mobile communication system. This mobile communication system is composed of a base station (hereinafter abbreviated as BS) 19 having a PHS 22 within a semi-public area 80, a PBX 16 having a semi-public roaming function and accommodating the BS 19, and a PIU (PHS Interface Unit) 13 connecting the PBX 16 to a mobile communication network 10.
The mobile communication network 10 accommodates a public base station 91 which exists in a public base station management area 90 and is connected to a fixed communication network 92 to form a public communication network 93.
The PHS 22 makes a position registration in the mobile communication network 10 through the BS 19, the PBX 16, and the PIU 13. The PHS 22 controls the call transmission, the call reception, or the like together with a mobile station (not shown) existing in the area 90 or a telephone 94 accommodated in the fixed communication network 92.
Namely, the PBX 16 mediates a position registration and a call from the PHS 22 existing in the semi-public area 80 not covered with a radio wave of the public base station 91 to the mobile communication network 10 and a call from the mobile communication network 10 to the PHS, thereby enabling communications therebetween.
FIG.53 shows a principle of the position registration by the semi-public roaming function of the PBX 16. BS""s 19 and 20 existing in general calling areas 81 and 82 respectively including PHS""s 22 and 23 are accommodated in the PBX 16. This PBX 16 controls all of the PHS""s existing in the semi-public area 80 including the areas 81 and 82 and is connected to the mobile communication network 10 through the PIU 13.
The PBX 16 makes a position registration in the mobile communication network 10 with a xe2x80x9cnormalizing call area No.xe2x80x9d corresponding to the general calling area where the PHS exists as PHS position information. The position information of the PHS""s 22 and 23, for instance, is supposed to have the xe2x80x9cnormalizing call area No.xe2x80x9d of e.g. xe2x80x9c1xe2x80x9d and xe2x80x9c2xe2x80x9d respectively corresponding to the general calling areas 81 and 82 where the PHS""s 22 and 23 exist for performing the position registration.
This will be described referring to a position registration sequence shown in FIG. 54. The BS 19 receives a SETUP message (position registering request) including a PS No. and the like from the PHS 22 to transmit the message to the PBX 16 (at step R10).
The PBX 16 returns a CALL-PROC message to the BS 19 and converts the SETUP message into a REGISTER message by the addition of the xe2x80x9cnormalizing call area No.xe2x80x9d=xe2x80x9c1xe2x80x9d corresponding to the general calling area 81 (the BS 19) where the PHS 22 exists to transmit the REGISTER message to the PIU 13.
The PIU 13 stores the xe2x80x9cnormalizing call area No.xe2x80x9d=xe2x80x9c1xe2x80x9d and transmits the REGISTER message excluding the xe2x80x9cnormalizing call area No.xe2x80x9d to the mobile communication network 10 to make the position registering request (at step R11).
Hereinafter, a FACILITY message (a certification request) from the mobile communication network 10 is converted into an INFO message at the PBX 16 to be sent to the BS 19 (and in turn the PHS 22) (at step R12), the INFO message (a certification response) from the BS 19 being converted into the FACILITY message to be transmitted to the mobile communication network 10 (at step R13), so that an REL-COMP message from the mobile communication network 10 is converted into a DISC message to be transmitted to the BS 19 (at step R14).
An REL message and the REL-COMP message are transmitted/received between the BS 19 and the PBX 16 to finish the position registration (at steps R15 and R16).
FIG. 55 shows a call reception sequence by the semi-public roaming function. When receiving a calling No., a called number, and the SETUP message (call reception request) including the PS No. from the mobile communication network 10, the PIU 13 prepares a SETUP message added with the xe2x80x9cnormalizing call area No.xe2x80x9d stored and transmits the SETUP message to the PBX 16.
The PBX 16 transmits the SETUP message excluding the xe2x80x9cnormalizing call area No.xe2x80x9d to the BS 19 (and in turn the PHS 22) corresponding to the xe2x80x9cnormalizing call area No.xe2x80x9d included in the received SETUP message (at step R20).
Hereinafter, the CALL-PROC message is transmitted from the BS 19 to the mobile communication network 10 (at step R21). After the messages of the certification request and the certification response are transmitted/received (at steps R22 and R23) in the same way as the position registering sequence, an ALERT message and a CONN message are sequentially transmitted from the BS 19 to the mobile communication network 10 (at steps R24 and R25). After a CONN-ACK message which is a response message of the CONN message is transmitted from the mobile communication network 10 to the BS 19 (at step R26), the communication is started (at step R27).
Next, a call transmission sequence by the semi-public roaming function will be described referring to FIG. 56.
The BS 19 transmits the SETUP message including the calling No., the called number and the PS No. to the mobile communication network 10 through the PBX 16 and the PIU 13 (at step R30). After transmitting the CALL-PROC message to the BS 19 (at step R31), the mobile communication network 10 transmits/receives the messages of the certification request and the certification response to/from the BS 19 (at steps R32 and R33).
After the ALERT message and the CONN message are transmitted from the mobile communication network 10 to the BS 19 through an RBT (Ring Back Tone) step (at steps R34, R35, and R36), the communication is started (at step R37).
When none of the PIU""s connected to the PBX 16 is available due to a fault, congestion, non-equipping, and the like in such a prior art mobile communication system, it become impossible to perform the position registration or the call transmission from the PHS 22 and the call reception to the PHS 22. Accordingly, the PHS 22 is not able to communicate with the mobile communication network 10 through the PBX 16 having the semi-public roaming function unless the PIU becomes available after recovering from the fault, relieving the congestion, being equipped, or the like.
It is accordingly an object of the present invention to provide a mobile communication system composed of a PBX connected to a mobile communication network and having a semi-public roaming function wherein communications are realized between a PHS and a mobile communication network through the PBX where a PIU is not equipped or is unavailable.
In order to achieve the above-mentioned object, a mobile communication system, according to claim 1, of the present invention comprises; a first exchange for accommodating a base station which communicates with a mobile station, and a second exchange having a semi-public roaming function connected to the first exchange with a leased circuit and connected to a mobile communication network through an interface unit; the first exchange having a converting means for converting position information of the mobile station as prestored therein into virtual position information peculiar to the mobile communication network and for transmitting the virtual position information to the interface unit through the second exchange, and the second exchange having a transmission setting means for setting a transmission of response information from the mobile communication network for the virtual position information to the first exchange.
According to claim 2, the first and the second exchanges may comprise PBX""s.
This will be described referring to an operation principle (1) shown in FIG. 1. The mobile communication system is composed of a base station (BS) 19, a mobile station (PHS) 22 within a management area 81 of the base station 19, a first private branch exchange (PBX) 16 accommodating the base station 19, a second PBX 17 connected to the PBX 16 through, e.g. leased circuit trunks (hereinafter simply referred to as leased circuit) 25 and 26, and an interface unit (PIU) 14 connecting the PBX 17 to a mobile communication network 10.
The PBX 16 and the PBX 17 respectively include the converting means and the transmitting setting means.
{circle around (1)} When the PBX 16 receives the position information from the PHS 22 through the base station 19, the converting means of the PBX 16 determines the position of the PHS 22 with an allocated number of the base station 19 being made a key and converts the position information into virtual position information peculiar to the mobile communication network 10 to transmit the same to the PBX 17 through the leased circuit 25.
{circle around (2)} The PBX 17 transmits the virtual position information received through the leased circuit 26 to the mobile communication network 10 through the PIU 14. At the same time, the transmitting setting means of the PBX 17 decides that the virtual position information is transmitted from a station other than itself and sets the transmission of the response information from the mobile communication network 10 for the virtual position information to the PBX 16 through the leased circuit 26.
This operation enables the position information of the PHS 22 within the management area 81 for the base station 19 to be transmitted to the mobile communication network 10 through the PBX 17 and the PIU 14 without being abandoned even when any PIU is not connected to the PBX 16 so that the response information for the position information from the mobile communication network 10 can be transmitted to the PBX 16 through the PBX 17 (see {circle around (3)} in FIG. 1).
Also, in the present invention according to claim 3, the position inform and the virtual position information may respectively comprise position registering information and virtual position registering information.
Namely, even when any PIU is not connected to the PBX 16 the position registering information of the PHS 22 can be converted into the virtual position registering information, transmitted to the mobile communication network 10 through the PBX 17 and the PIU 14 without being abandoned so that the response information for the position registering information from the mobile communication network 10 can be transmitted to the PHS 22 through the PIU 14 and the PBX 17.
Also, in the present invention according to claim 4, the position information and the virtual position information may respectively comprise calling information and virtual calling information including the position registering information.
Namely, also in the calling information including the position registering information similar to that of claim 3, the converting means of the PBX 16 prepares the virtual calling information which is the position information included in the calling information from the PHS 22 and converted into the virtual position information, and transmits the virtual calling information to the PBX 17. The PBX 17 transmits the virtual calling information to the mobile communication network 10 through the PIU 14. At the same time the transmitting setting means of the PBX 17 sets the transmission of the response information corresponding to the virtual calling information to the PBX 16.
This operation makes it possible for the PBX 16 to transmit/receive the calling information and the response information between the PBX 16 and the mobile communication network 10 through the PBX 17.
Also, in the present invention according to claim 5, the converting means may invert the virtual position information into the position information.
Namely, the converting means of the PBX 16 inverts the virtual position information included in the response information sent from the mobile communication network 10 to the PBX 16 through the PBX 17 into the position information so that the response information can be transmitted to the PHS 22 based on the position information (see {circle around (4)} in FIG. 1).
Also, in the present invention according to claim 6, the transmission setting means may set a transmission of called information addressed to the mobile station position-registered from the mobile communication network to the first PBX.
Namely, the transmitting setting means of the PBX 17 sets the transmission of the called information addressed to the position-registered PHS 22 to the PBX 16.
This operation makes it possible for the PBX 17 to transmit the called information addressed to the PHS 22 position-registered as to the management area 81 of the BS 19 to the PBX 16 (see {circle around (3)} in FIG. 1).
Also, in the present invention according to claim 7, the first PBX may be connected to the mobile communication network through an interface unit the first PBX itself accommodates to perform the semi-public roaming function, and the first PBX may have a decision means for deciding whether or not its own interface unit is available, transmit the position information to the mobile communication network through its own interface unit when the interface unit is available, and transmit the position information to the mobile communication network through the second PBX when the interface unit is unavailable.
This will be described referring to an operation principle (2) shown in FIG. 2. This mobile communication system is different from that shown in FIG. 1 in that the first PBX 16 accommodates a PIU 13 connected to the mobile communication network 10 and has a decision means for deciding whether or not the PIU 13 is available.
In operation, when the position information is transmitted to the mobile communication network 10, the decision means in the PBX 16 decides whether or not the PIU 13 is available. When the PIU 13 is available, the position information is transmitted through the PIU 13 to the mobile communication network 10 (see {circle around (1)} in FIG. 2). When the PIU 13 is unavailable, the position information is transmitted through the second PBX 17 to the mobile communication network 10 as mentioned above (see {circle around (2)} in FIG. 2).
This operation makes it possible to transmit the position information through the second PBX 17 even when the PIU 13 can not be used because of a fault or congestion.
Also, in the present invention according to claim 8, the first PBX may be connected to a plurality of PBX""s which accommodate the interface unit of the mobile communication network with a leased circuit, and when its own interface unit is not available, the decision means may decide whether or not the leased circuit is available and transmit the position information through the available leased circuit.
This will be described referring to an operation principle (3) shown in FIG. 3. This mobile communication system is different from that shown in FIG. 2 in that a PBX 18 which accommodates a PIU 15 connected to the mobile communication network 10 is connected to the PBX 16 through leased circuits 27 and 28.
In operation, when the PIU 13 of its own station is unavailable (see {circle around (1)} in FIG. 3), the decision means of the PBX 16 decides whether or not the leased circuits 25 and 27 are available. Then the position information is transmitted through an available leased circuit, e.g. the leased circuit 27 (see {circle around (2)}, {circle around (3)} in FIG. 3). The operation of the PBX 18 is the same as that of the PBX 17 shown in FIG. 2.
This operation makes it possible for the PBX 16 to transmit the position information of the PHS 22 to the mobile communication network 10 through the PBX connected to the available leased circuit when the PIU 13 which the PBX 16 accommodates is unavailable.
Also, in the present invention according to claim 9, the first PBX may include a means for transmitting an inquiry message inquiring whether or not the accommodated interface unit is available to another PBX through the leased circuit, and a PBX which has received the inquiry message may have a means for returning a response message for the inquiry message.
This will be described referring to an operation principle (4) shown in FIG. 4. This mobile communication system is different from that shown in FIG. 3 in that the PBX 16 has a PIU status inquiring means inquiring whether or not the PIU""s 14 and 15 respectively connected to the PBX""s 17 and 18 are available and that the PBX""s 17 and 18 respectively have a PIU status response means responding the status of the PIU""s 14 and 15.
In operation, when the PIU 13 is unavailable (see {circle around (1)} in FIG. 4), the PIU status inquiring means of the PBX 16 transmits to the PBX""s 17 and 18 messages respectively inquiring whether or not the accommodated PIU""s 14 and 15 are available through the leased circuits 25 and 27 (see {circle around (2)} in FIG. 4). The PIU status response means of the PBX""s 17 and 18 which have received the messages returns the response message indicating whether or not their own PIU""s are available to the PBX 16 (see {circle around (3)} in FIG. 4). The PBX 16 transmits the above-mentioned position information to a PBX which has indicated that its own PIU is available.
This operation makes it possible for the PBX 16 to transmit the position information through the PBX accommodating the available PIU. Accordingly, even when the position information is sent to a PBX in which the leased circuit is available but the accommodated PIU is unavailable, the position information is prevented from being abandoned.
Also, in the present invention according to claim 10, PBX""s except the first PBX may have a means for notifying the first PBX of unit status information indicating whether or not the accommodated interface unit is available, and the first PBX may have a means for transmitting the position information to a PBX which stores the unit status information and accommodates the available interface unit.
This will be described referring to an operation principle (5) shown in FIG. 5. This mobile communication system is different from that shown in FIG. 4 is that the PBX""s 17 and 18 respectively have PIU status notifying means which notify the PBX 16 whether or not their own PIU""s 14 and 15 are available and that the PBX 16 has a PIU status storage means for storing the PIU statuses of the PBX""s 17 and 18.
In operation, the PIU status notifying means of the PBX""s 17 and 18 notify the PBX 16 of the status indicating whether or not their own PIU""s are available (see {circle around (1)} in FIG. 5). The PIU status storage means of the PBX 16 stores the statuses of the PIU""s 14 and 15 which have received the notification. When the PBX 16 can not use its own PIU 13 (see {circle around (2)} in FIG. 5), the PBX 16 transmits the position information to the mobile communication network 10 through a PBX having an available PIU based on the PIU status storage means.
This operation makes it possible to prevent the position information from being sent to an PBX accommodating an unavailable PIU and being abandoned by referring to the PIU status storage means without inquiring statuses of the PIU""s accommodated in the PBX""s 17 and 18.
Also, in the present invention according to claim 11, the first PBX may have a means for selecting a PBX which accommodates the interface unit based on a preset priority.
This will be described referring to a principle (6) shown in FIG. 6. This mobile communication system is different from that shown in FIG. 3 in that the PBS 16 has a selecting means instead of the decision means.
Namely, the selecting means of the PBS 16 selects a PBX according to a preset priority and transmits the position information to the mobile communication network 10 through a selected PBX (see {circle around (1)}, {circle around (2)} in FIG. 6).
This operation makes it possible for a maintenance person to transmit the position information to the mobile communication network 10 through a preset PBX and to provide fine and careful services.
Also, in the present invention according to claim 12, the first PBX may have a means for sequentially and equally selecting a PBX which accommodates the interface unit.
Namely, with the selecting means shown in FIG. 6 the PBX 16 can select the PBX""s 17 and 18 connected to the PBX 16 not according to the priority but sequentially.
This operation makes it possible to disperse a load by equally selecting the PBX""s 17 and 18.
Also, in the present invention according to claim 13, the first PBX may have a means for selecting another PBX which forms a transmission object of the position information according to a preset time zone.
Namely, the selecting means shown in FIG. 6 presets a time zone when the PBX""s 17 and 18 are substituted for the priority. According to this presetting, the selecting means selects the PBX and sends the position information to the mobile communication network 10 through the selected PBX.
Also, in the present invention according to claim 14, the first PBX may have a means for transmitting the position information through an interface unit of another PBX when the circuit available number of its own present interface unit is more than a preset circuit available number.
This will be described referring to an operation principle (7) shown in FIG. 7. This mobile communication system is different from that shown in FIG. 2 in that the PBX 16 has an available PIU circuit number-management means instead of the decision means.
Namely, the management means compares a circuit number presently used at the PIU 13 with a preset available circuit number and controls the circuit to transmit the position information through another interface unit when an occupied circuit number is larger than the available circuit number.
This operation makes it possible to perform the position registration or the call transmission request through the leased circuit and the PIU of another PBX and to disperse the load when the available circuit of the PIU 13 has reached a fixed usage status.
Also, in the present invention according to claim 15, the first PBX may accommodate a plurality of base stations and may have a means for designating a PBX to which the position information is transmitted for each base station.
This will be described referring to an operation principle (8) shown in FIG. 8. This mobile communication system is different from that shown in FIG. 2 in that the PBX 16 further accommodates a BS 20, a PHS 23 exists in a management area 82 in the BS 20, and a management means is included instead of the decision means.
In operation, a corresponding relationship between the BS""s 19, 20 and the PBX""s including the PBX 16 is preset in the management means. When the position information is received from the BS 19, for instance, the management means transmits the received position information to the mobile communication network 10 through its own PIU 13 corresponding to the BS 19 (see {circle around (1)} in FIG. 8). When the position information is received from the BS 20, the management means transmits the position information through the PBX 17 corresponding to the BS 20 (see {circle around (2)} in FIG. 8).
This operation makes it possible to select an available PBX used per BS, to further select a PIU, and to disperse the load within the mobile communication system.
Also, in the present invention according to claim 16, the mobile station and the interface unit respectively may comprise a PHS and a PHS interface unit.